Public Sub Chart_AddLabels()
Dim schartname As String
   schartname = Right(ActiveChart.Name, Len(ActiveChart.Name) - Len(ActiveSheet.Name) - 1)
   Set rgerange = Application.InputBox("Select the labels to add", Type:=8)
   snewlabel = rgerange.Address
   ActiveSheet.ChartObjects(schartname).Activate
   Call Chart_DataLabelsAdd(1, rgerange.Column, _
                               rgerange.Row, _
                               rgerange.Row + rgerange.Rows.Count - 1)
End Sub

Public Sub Chart_DataLabelsAdd(iSeriesNo As Integer, _
                               iColFirst As Integer, _
                               lRowFirst As Long, _
                               lRowLast As Long)
Dim rgerange As Range
Dim lcount As Long
Dim snewlabel As String
Dim lsmallest As Long
   ActiveChart.SeriesCollection(iSeriesNo).ApplyDataLabels Type:=xlDataLabelsShowLabel
   If ActiveChart.SeriesCollection(iSeriesNo).DataLabels.Count <= (lRowLast - lRowFirst + 1) Then
      lsmallest = ActiveChart.SeriesCollection(1).DataLabels.Count
   End If
   If (lRowLast - lRowFirst) <= ActiveChart.SeriesCollection(1).DataLabels.Count Then
      lsmallest = lRowLast - lRowFirst + 1
   End If
   For lcount = 1 To lsmallest
      snewlabel = ActiveSheet.Cells(lRowFirst + lcount - 1, iColFirst).Value
      ActiveChart.SeriesCollection(iSeriesNo).DataLabels.Select
      ActiveChart.SeriesCollection(iSeriesNo).Points(lcount).DataLabel.Select
      Selection.Characters.Text = snewlabel
   Next lcount
End Sub